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- Author or Editor: Robert K. Prange x
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Larvae of the blueberry maggot (Rhagoletis mendax Curran) were raised on apples (Malus domestics Borkh. cv. Idared), and exposed larvae were treated 48 hours with CO concentrations ranging from 0% to 100% at O concentrations of 2%, 5%, or 20% (0% for the 100% CO) at 5 or 21C. Blueberry maggot survival was reduced to 10% when the larvae were subjected to CO concentrations > 45% at 21C. Fumigation was more effective at 21C than at 5C. Oxygen at 2% or 5% did not reduce larval survival when compared with treatments containing 20% O. In a separate experiment, six commercial shipments, each consisting of four hundred eighty 0.5-liter containers of infested lowbush blueberries (Vaccinium angustlfolium Ait.), were placed in a large fiberglass tank and fumigated with 54% CO at 21C. The blueberries were sampled for quality and larval survival after 24 and 48 hours of CO treatment. Atter 48 hours, 9% of the blueberry maggots in infested blueberries survived fumigation with 54% CO, while 68% of maggots survived in air. The quality of fumigated lowbush blueberries was not adversely affected by fumigation with 54% CO for up to 48 hours, as indicated by marketable berries, berry weight, split berries, shriveled berries, epicuticular wax (bloom), firmness, soluble solids and titratable acid concentrations, offflavors, and skin browning.
Postharvest quality and sensory attributes of organically and conventionally grown `McIntosh' and `Cortland' apples (Malus domestica Borkh.) stored at 3C in ambient air or in controlled atmospheres were evaluated. Organically grown apples had higher soluble solids concentration than conventionally grown apples, while there were no significant differences in firmness or titratable acids content. Organically grown `McIntosh' were perceived by sensory panelists as firmer than conventionally grown `McIntosh' at harvest but not after storage, which may have been due to maturity differences. No significant differences were perceived in juiciness, sweetness, tartness, and off-flavor of apples at harvest or after storage.
Previous studies have shown that the fry color of stored potatoes (Solanum tuberosum L.) can be negatively affected by an interaction between elevated CO2 (2 kPa) and ethylene gas (0.5 μL·L− 1) from various sources. Two consecutive trials were conducted during each of two storage seasons (2006 and 2007) to study the effects of varying concentrations of these two gases. In each year, CO2 at 0, 0.5, 1.0, or 2.0 kPa plus 0, 0.25, or 0.5 μL·L− 1 ethylene was applied in a factorial design to ‘Russet Burbank’ tubers for 9 weeks. Trials that began in Jan. 2006 and Jan. 2007 comprised the dormant-tuber experiment; trials that began in Apr. 2006 and Apr. 2007 comprised the nondormant-tuber experiment. Fry color of the tubers was evaluated at the start of each trial and thereafter at intervals of 3 weeks. In all trials, when tubers were exposed to different concentrations of CO2 but without ethylene, fry color was the same as in untreated controls. When only ethylene was applied, the fry color was 7 to 22 Agtron percent reflectance units darker than the controls. In the nondormant-tuber experiment, the darkening resulting from ethylene was dose-related, in agreement with previous research. When the tubers were exposed to both CO2 and ethylene, dose-related responses to both gases were observed in the nondormant-tuber experiment, i.e., fry color was darker with an increase in either CO2 or ethylene when both gases were present. Neither the dose–response to ethylene nor the interaction between ethylene and CO2 was statistically significant in the dormant-tuber experiment. In both experiments, the darkest color was observed when both gases were present at the highest concentrations. A dose–response of potato fry color to CO2 in the presence of ethylene has not been reported previously.
In a 2-year study, `McIntosh' apples were stored in a CA regime of 4.5% CO2 + 2.5% O2. Within the CA cabinets there were three humidity levels: >75% RH (CaCl2 salt in the chamber), >90% RH (ambient), or >95% RH (distilled water in the chamber). After removal at 4 and 8 months, the fruit were warmed to handling temperatures of 0C, 10C, or 20C and subjected to three levels of impact bruising of 0, 10, or 20 lb with a Ballauf pressure tester with a 1.5 × 1.5-cm tip. The results showed that low-humidity CA storage decreased visible bruising. Although visible shrivel was not observed, the low-humidity treatment may increase the possibility of its occurrence. Respiration, measured as O2 consumption or CO2 production immediately after removal from CA storage, was lowest in low humidity (>75% RH) and highest in ambient humidity (>90% RH) CA storage. The humidity treatments did not affect firmness, soluble solids, titratable acids, or ethylene production. Increasing the temperature during post-storage handling decreased the amount of visible bruising without affecting other variates such as firmness, soluble solids, titratable acids, respiration, or ethylene production.
`Redcort Cortland' and `Redmax' and `Summerland McIntosh' apples (Malus ×domestica Borkh.) were treated with 900 nL·L-1 of 1-methylcyclopropene (1-MCP) for 24 hours at 20 °C before storage and were kept at 3 °C in either a controlled atmosphere (CA) of 2 kPa O2 and <2.5 kPa CO2 or in an air (RA) environment for up to 9 months. After 4.5 months, half of the fruit were treated with a second 900 nL·L-1 1-MCP application in air at 3 °C for 24 hours and then returned to RA or CA storage. At harvest and following removal at 3, 6, and 9 months and a 7-day shelf life at 20 °C, fruit firmness, titratable acidity (TA) and soluble solids content (SSC) were measured, while internal ethylene concentrations (IEC) in the apple core were quantified after 1 day at 20 °C. Upon storage removal and following a 21-day shelf life at 20 °C, disorder incidence was evaluated. 1-MCP-treated apples, particularly those held in CA-storage, were more firm and had lower IEC than untreated fruit. Higher TA levels were maintained with 1-MCP in all three strains from both storages, while SSC was not affected. Following the 6- and/or 9-month removals, 1-MCP suppressed superficial scald development in all strains and reduced core browning and senescent breakdown in RA-stored `Redmax' and `Summerland' and senescent breakdown in RA-stored `Redcort'. 1-MCP generally maintained the quality of `Cortland' and `McIntosh' fruit held in CA and RA environments (particularly the former) to a higher degree than untreated apples over the 9-month storage period. A second midstorage application of 1-MCP at 3 °C did not improve poststorage fruit quality above a single, prestorage treatment.
In three consecutive years of storage trials, the effects of reduced O2 levels, elevated CO2 levels, and ethylene on the fry color and sugar content [sucrose and reducing sugars (glucose and fructose)] of `Russet Burbank' potato (Solanumtuberosum L.) tubers were evaluated. The potatoes were stored in modified atmosphere chambers and the atmosphere mixtures were supplied from compressed gas cylinders. Fry color and sugar content were assessed at the start of each trial and after several weeks of exposure to the treatment atmospheres. Four 4-week trials were conducted in 2002 and two 9-week trials were conducted in each of 2003 and 2004. No differences in fry color or sugar content attributable to either increased CO2 or decreased O2 were observed, compared with untreated controls, in any year. In the second and third years, only selected treatments were repeated, with or without 0.5 μL·L-1 ethylene. Ethylene alone caused a moderate darkening of fry color and an increase in reducing sugars. However, the fry color and reducing sugar content of tubers exposed to a combination of elevated CO2 and ethylene were considerably darker and higher, respectively, than observed with ethylene alone. No similar interaction between ethylene and O2 level was observed. These results suggest that CO2 promoted ethylene-induced fry color darkening, which may explain the contradictory effects of CO2 on fry color frequently observed by the potato industry. This is contrary to published research on other fruits and vegetables, which has generally shown that CO2 inhibits ethylene action.
Chlorophyll fluorescence was evaluated as a rapid and nondestructive technique to detect low-O2 or high-CO2 stress in apples (Malus domestica Borkh.) during storage. `Marshall' McIntosh apples were held for 5, 10, 15, 20, or 25 days at 3C in 1) standard O2 (2.5% to 3%) and low CO2 (<1%), 2) low O2 (1% to 1.5%) and low CO2 (<1%), 3) standard O2 (2.5% to 3%) and standard CO2 (4% to 4.5%), or 4) standard O2 (2.5% to 3%) and high CO2 (11% to 12%). Only 10% of the apples had skin discoloration after 5 days in 1% to 1.5% O2; 80% developed skin discoloration after 20 days in low O2. Small desiccated cavities in the cortex, associated with CO2 injury, developed in 10% of the apples after 20 days in 11% to 12% CO2. Five days in 1% to 1.5% O2 or 11% to 12% CO2 caused variable fluorescence (Fv) of apple fruit to decrease compared to those held in standard atmospheres. Additional exposure did not significantly affect Fv in either the low-O2 (1% to 1.5%) or high-CO2 (11% to 12%) treatment. Our results suggest that chlorophyll fluorescence techniques can detect low-O2 and high-CO2 stress in apples before the development of associated disorders.
A final harvest window (FHW), expressed as Streif Index coefficients [firmness/(percentage soluble solids concentration × starch index)], was developed for identifying maximum fruit quality for strains of `McIntosh', `Cortland', and `Jonagold' apples (Malus ×domestica Borkh.) following 8 months of controlled-atmosphere (CA) storage. The Streif Index was calculated during nine preharvest (twice per week) intervals and four weekly harvests over three seasons. The relationship between Streif Index (dependent variable) and day of year (independent variable) of the preharvest and harvest samples was then derived by negative first-order linear regression equations that had parameter estimate (b1) probability values ≤0.0001 for all of the strains. Apples from the four harvest periods were stored in standard CA storage for 8 months and then subjected to a 7-day shelf-life test at 0 °C followed by 5 days at 20 °C. Poststorage quality data were categorized and combined to produce an overall fruit quality rating scale. For each strain, the final harvest (i.e., day of year) was identified as that which directly preceded at least a 10% drop in the poststorage fruit quality rating compared with the first harvest rating. The FHW, expressed as Streif Index coefficients via the regression of Streif Index (Y) on day of year (X), was then calculated as the 3-year final harvest mean with the upper and lower window limits being determined by the standard deviation of the mean. The lower to upper FHW boundaries ranged from 4.18 to 5.34, 4.12 to 5.46, 4.51 to 5.68, 5.23 to 5.99, and 1.38 to 2.34 for Redmax, Marshall and Summerland `McIntosh', Redcort `Cortland' and Wilmuta `Jonagold', respectively. The practical utility of the Streif Index method lies in the ease with which apple fruit maturity at harvest can be evaluated for its suitability for long-term CA storage.
To determine if postharvest treatments of 1-methylcyclopropene (1-MCP) retard the senescence of highbush blueberries (Vaccinium corymbosum L.) removed from storage, `Burlington' (early) and `Coville' (late) fruit were harvested from four experimental sites and treated for 24 hours at 20 °C with 0 (control), 25 (low), 100 (medium), or 400 (high) nL·L-1 of 1-MCP. All fruit were then stored in a controlled atmosphere of 10-15 kPa O2 and 10 kPa CO2 at -1 to 1 °C for 4, 8, and 12 weeks, followed by a 20 °C shelf-life of up to 20 days. During the shelf-life period immediately after harvest and those following each storage removal, percent marketable fruit (PMF) were calculated daily as: [fruit in good condition]/[total berry number] × 100. Changes in PMF were not affected by 1-MCP treatment; hence, we conclude that 1-MCP at rates up to 400 nL·L-1 does not alter the shelf-life quality of the highbush blueberry cultivars tested.